Evaluation of the hypoglycaemic activity of Petiveria alliacea (Guinea Hen Weed) extracts in normoglycaemic and diabetic rat models / Evaluación de la actividad hipoglicémica de los extractos de Petiveria alliacea (Yerba de Guinea o Anamú) en modelos de ratas diabéticas y normoglicémicase

OBJECTIVE: Petiveria alliacea (p alliacea) has ethno-traditional use as a hypoglycaemic agent in Jamaica and is yet to be scientifically validated as such. Therefore, extracts of aerial parts of the plant were evaluated for hypoglycaemic activity in normoglycaemic and diabetic rats. METHODS: Aqueous and hexane extracts prepared from leaves of p alliacea were tested for hypoglycaemic activity. An acute administration of the extracts (200 and 400 mg/kg body weight) was evaluated in normoglycaemic rats. Additionally, the hypoglycaemic effect ofsub-chronic administration was assessed in streptozotocin-induced diabetic rats. Blood glucose was recorded using a glucometer and test strips. Data were analysed using Student's t-test (p < 0.05). RESULTS: The aqueous and hexane extracts demonstrated no significant reduction of fasting blood glucose (FBG) and no significant improvement of glucose tolerance in normal rats. The aqueous extract (400 mg/kg body weight) increased FBG from 4.75 ± 0.28 mmol/L to 5.88 ± 0.46 when compared to control (p < 0.001). In diabetic rats, the hexane extract (400 mg/kg body weight) caused reduction of FBG after two weeks of treatment (p < 0.010), but this was not sustained. The aqueous extract showed no reduction of FBG in diabetic rats. CONCLUSION: The aqueous extract of p alliacea demonstrated a hyperglycaemic effect in normoglycaemic rats and showed no hypoglycaemic activity in diabetic rats. The hexane extract caused no hypoglycaemic action in normal rats and failed to sustain an initial hypoglycaemic action in diabetic rats. This study presents evidence that does not support significant hypoglycaemic activity of p alliacea; this could hold significant implications for its use in ethno-traditional medicine.

OBJETIVO: Petiveria alliacea (p alliacea) tiene uso etnotradicional como agente hipoglicémico en Jamaica, y todavía requiere ser validado científicamente. Por lo tanto, extractos de las partes aéreas de la planta fueron evaluados en relación con su actividad hipoglicémica en ratas normoglicémicas y diabéticas. MÉTODOS: Extractos acuosos y extractos de hexanos preparados a partir de hojas de p alliacea fueron sometidos a prueba a fin de detectar su actividad hipoglicémica. Se evaluó el efecto de una administración aguda de los extractos (200 y 400 mg/kg de peso corporal) en ratas normoglicémicas. Además, se evaluó el efecto hipoglicémico de la administración subcrónica en ratas con diabetes inducida por estreptozotocina. La glucosa en sangre fue registrada usando un glucómetro y tiras reactivas. Los datos se analizaron mediante la prueba t de Student (p < 0.05). RESULTADOS: Los extractos acuosos y los extractos de hexano no mostraron reducción significativa alguna de la glucemia en ayunas (GA), ni tampoco ninguna mejora significativa de la tolerancia a la glucosa en ratas normales. El extracto acuoso (400 mg/kg de peso corporal) aumentó la GA de 4,75 ± 0,28 mmol/L a 5,88 ± 0,46 en comparación con el control (p < 0.001). En las ratas diabéticas, el extracto de hexano (400 mg/kg de peso corporal), trajo por consecuencia la reducción de GA tras dos semanas de tratamiento (p < 0.010), pero este efecto no se mantiene. El extracto acuoso no mostró ninguna reducción de GA en las ratas diabéticas. CONCLUSIÓN: El extracto acuoso de p alliacea mostró un efecto hiperglicémico en las ratas normoglicémicas, y no mostró ninguna actividad hipoglicémica en las ratas diabéticas. El extracto de hexano no produjo ninguna acción hipoglicémica en ratas normales, y no mantuvo la acción hipoglicémica inicial en las ratas diabéticas. Este estudio presenta evidencias que no respaldan una actividad hipoglicémica significativa de p alliacea, lo cual podría tener importantes implicaciones para su uso en la medicina etnotradicional.

Evaluation of the Hypoglycaemic Activity of Petiveria alliacea (Guinea Hen Weed) Extracts in Normoglycaemic and Diabetic Rat Models.

OBJECTIVE: Petiveria alliacea (P alliacea) has ethno-traditional use as a hypoglycaemic agent in Jamaica and is yet to be scientifically validated as such. Therefore, extracts of aerial parts of the plant were evaluated for hypoglycaemic activity in normoglycaemic and diabetic rats. METHOD: Aqueous and hexane extracts prepared from leaves of P alliacea were tested for hypoglycaemic activity. An acute administration of the extracts (200 and 400 mg/kg body weight) was evaluated in normoglycaemic rats. Additionally, the hypoglycaemic effect of sub-chronic administration was assessed in streptozotocin-induced diabetic rats. Blood glucose was recorded using a glucometer and test strips. Data were analysed using Student's t-test (p ≤ 0.05). RESULTS: The aqueous and hexane extracts demonstrated no significant reduction of fasting blood glucose (FBG) and no significant improvement of glucose tolerance in normal rats. The aqueous extract (400 mg/kg body weight) increased FBG from 4.75 ± 0.28 mmol/L to 5.88 ± 0.46 when compared to control (p ≤ 0.001). In diabetic rats, the hexane extract (400 mg/kg body weight) caused reduction of FBG after two weeks of treatment (p ≤ 0.010), but this was not sustained. The aqueous extract showed no reduction of FBG in diabetic rats. CONCLUSION: The aqueous extract of P alliacea demonstrated a hyperglycaemic effect in normoglycaemic rats and showed no hypoglycaemic activity in diabetic rats. The hexane extract caused no hypoglycaemic action in normal rats and failed to sustain an initial hypoglycaemic action in diabetic rats. This study presents evidence that does not support significant hypoglycaemic activity of P alliacea; this could hold significant implications for its use in ethno-traditional medicine.

Estimation of energy expenditure in free-living red deer (Cervus elaphus) with the doubly-labelled water method.

Energy expenditure was estimated using the doubly-labelled water (DLW) method in summer in five free-living adult, non-pregnant, non-lactating, red deer (Cervus elaphus) hinds (weight 107.3 (SE 0.9) kg; age 6 (SE 1) years) on lowland pasture under typical farming conditions. Climatic conditions were monitored throughout the experiment. Errors due to 2H losses in CH4 and faeces were calculated from previous estimates of stoichiometries. CH4 production, fractionated water loss, urinary N and O2 consumption were estimated using an iterative approach. The water flux (rH2O) in these animals consuming only fresh grass was 12 (SE 0.5) kg/d, the CO2 production (rCO2) was 1271 (SE 40) litres/d and the mean energy expenditure was 25 (SE 0.8) MJ/d. There were no significant differences in the isotope distribution spaces and flux rates, rH2O, rCO2 or energy expenditure using the multi-point or two-point approaches to calculation. The DLW-derived energy expenditure of 25 MJ/d is approximately 20% higher than the recommended intake of 21 MJ/d for adult hinds kept outdoors (Adam, 1986) and, at 757 kJ/kg0.75 per d, one third higher than the value of 570 kJ/kg0.75 per d for stags penned indoors (Key et al. 1984).

Validation of the doubly labeled water method in growing pigs.

The CO2 production (rCO2) of eight growing pigs was determined by continuous collection of CO2 over 21 days and simultaneously estimated using the doubly labeled water (DLW) method. The aim was to assess the accuracy of the method before and after correction for known sources of error and to test for any residual discrepancy arising from as yet unidentified sources of error. Mass spectrometer accuracy was verified by analyzing serial dilutions of the dose material in the form of an artificial decay curve; no significant bias was detected. The physiological errors were linearly dependent on weight gain. DLW-derived rCO2 (corrected only for fractionated water loss) underestimated the true value by 0.270 l CO2/g wt gain or -8% in the restricted (group R) and -16% in the ad libitum-fed (group AL) groups. Known sources of error accounted for -0.006 (methane), -0.032 (fecal 2H losses), -0.108 (fat synthesis), and -0.146 (changing pool size) l CO2/g wt gain. After correction for these sources of error the DLW-derived rCO2 differed from the true value by -2 +/- 3% in group R and 0 +/- 3% in group AL. Thus there was no significant bias in the DLW method after correction for known sources of error, even during rapid weight gain or at weight stability with or without correction. The precision estimates include both dose and background errors and uncertainty in the correction factors used. Strategies for optimizing precision are presented.

Water hydrogen incorporation into body fat in pigs: effect on double/triple-labeled water method.

A basic assumption of the doubly labeled water (DLW) and triply labeled water (TLW) methods for measuring water flux (rH2O), CO2 production (rCO2), and fractionated water loss (X) is that the H of body water only leaves the body as water. Any loss of isotopes in other products will introduce an error into these techniques. The body fat represents the largest potential sink for water H. 2H sequestration into the carcass fatty acids was investigated in eight pigs labeled with 2H2O for 21 days. rCO2 was measured simultaneously in respiration chambers to allow an accurate assessment of the effect of 2H sequestration on the estimated rCO2. The fat content of the diet (1.63%), level of intake, and stage of maturity were all designed to give the widest possible range of sequestration effects. Four animals were restricted to their estimated maintenance requirement and four were allowed to feed ad libitum giving a range of weight gain from 100 to 650 g/day. This was reflected in the estimated error on rH2O (+0.42% in the restricted group and +2.52% in the fast-growing animals) and on rCO2 (-1.30 and -7.59%, respectively). The error on the calculation of X using TLW was +0.03 units in the restricted group and +0.20 units in the fast-growing animals. The error of +0.2 on X propagates through to an underestimate of rCO2 of approximately 4%, and since this is additive with the error on DLW the ultimate error on rCO2 using TLW would be approximately -12%.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of the rates of acetyl-CoA hydrolysis and synthesis from acetate in rat hepatocytes and the role of these fluxes in substrate cycling.

1. Acetyl-CoA hydrolysis, acetyl-CoA synthesis from acetate and several related fluxes were measured in rat hepatocytes. 2. In contrast with acetyl-CoA hydrolysis, most of the acetyl-CoA synthesis from acetate occurred in the mitochondria. 3. Acetyl-CoA hydrolysis was not significantly affected by 24 h starvation or (-)-hydroxycitrate. 4. In the cytoplasm there was a net flux of acetyl-CoA to acetate, and substrate cycling between acetate and acetyl-CoA in this compartment was very low, accounting for less than 0.1% of the total heat production by the animal. 5. A larger cycle, involving mitochondrial and cytoplasmic acetate and acetyl-CoA, may operate in fed animals, but would account for only approx 1% of total heat production. 6. It is proposed that the opposing fluxes of mitochondrial acetate utilization and cytoplasmic net acetate production may provide sensitivity, feedback and buffering, even when these fluxes are not linked to form a conventional substrate cycle.